// addrspace.cc 
//	Routines to manage address spaces (executing user programs).
//
//	In order to run a user program, you must:
//
//	1. link with the -N -T 0 option 
//	2. run coff2noff to convert the object file to Nachos format
//		(Nachos object code format is essentially just a simpler
//		version of the UNIX executable object code format)
//	3. load the NOFF file into the Nachos file system
//		(if you haven't implemented the file system yet, you
//		don't need to do this last step)
//
// Copyright (c) 1992-1993 The Regents of the University of California.
// All rights reserved.  See copyright.h for copyright notice and limitation 
// of liability and disclaimer of warranty provisions.

#include "copyright.h"
#include "system.h"
#include "addrspace.h"
#include "noff.h"
#include "table.h"
#include "synch.h"

extern "C" { int bzero(char *, int); };

Table::Table(int s) : map(s), table(0), lock(0), size(s) {
    table = new void *[size];
    lock = new Lock("TableLock");
}

Table::~Table() {
    if (table) {
	delete table;
	table = 0;
    }
    if (lock) {
	delete lock;
	lock = 0;
    }
}

void *Table::Get(int i) {
    // Return the element associated with the given if, or 0 if
    // there is none.

    return (i >=0 && i < size && map.Test(i)) ? table[i] : 0;
}

int Table::Put(void *f) {
    // Put the element in the table and return the slot it used.  Use a
    // lock so 2 files don't get the same space.
    int i;	// to find the next slot

    lock->Acquire();
    i = map.Find();
    lock->Release();
    if ( i != -1)
	table[i] = f;
    return i;
}

void Table::Update(int i, void *f) {
	// Replaces the element at index i with the element.
	
	lock->Acquire();
	if ( map.Test(i)) {
		table[i] = f;
	}
	lock->Release();
}

void *Table::Remove(int i) {
    // Remove the element associated with identifier i from the table,
    // and return it.

    void *f =0;

    if ( i >= 0 && i < size ) {
	lock->Acquire();
	if ( map.Test(i) ) {
	    map.Clear(i);
	    f = table[i];
	    table[i] = 0;
	}
	lock->Release();
    }
    return f;
}

int Table::NumFilled() {
	return size - map.NumClear();
}

//----------------------------------------------------------------------
// SwapHeader
// 	Do little endian to big endian conversion on the bytes in the 
//	object file header, in case the file was generated on a little
//	endian machine, and we're now running on a big endian machine.
//----------------------------------------------------------------------

static void 
SwapHeader (NoffHeader *noffH)
{
	noffH->noffMagic = WordToHost(noffH->noffMagic);
	noffH->code.size = WordToHost(noffH->code.size);
	noffH->code.virtualAddr = WordToHost(noffH->code.virtualAddr);
	noffH->code.inFileAddr = WordToHost(noffH->code.inFileAddr);
	noffH->initData.size = WordToHost(noffH->initData.size);
	noffH->initData.virtualAddr = WordToHost(noffH->initData.virtualAddr);
	noffH->initData.inFileAddr = WordToHost(noffH->initData.inFileAddr);
	noffH->uninitData.size = WordToHost(noffH->uninitData.size);
	noffH->uninitData.virtualAddr = WordToHost(noffH->uninitData.virtualAddr);
	noffH->uninitData.inFileAddr = WordToHost(noffH->uninitData.inFileAddr);
}

//----------------------------------------------------------------------
// AddrSpace::AddrSpace
// 	Create an address space to run a user program.
//	Load the program from a file "executable", and set everything
//	up so that we can start executing user instructions.
//
//	Assumes that the object code file is in NOFF format.
//
//	"executable" is the file containing the object code to load into memory
//
//      It's possible to fail to fully construct the address space for
//      several reasons, including being unable to allocate memory,
//      and being unable to read key parts of the executable.
//      Incompletely consretucted address spaces have the member
//      constructed set to false.
//----------------------------------------------------------------------

AddrSpace::AddrSpace(OpenFile *executable) : fileTable(MaxOpenFiles), stackMap(MAX_THREADS) { // magic number should remove
    NoffHeader noffH;
    unsigned int i, size;
	processID = -1;
	
    // Don't allocate the input or output to disk files
    fileTable.Put(0);
    fileTable.Put(0);

    executable->ReadAt((char *)&noffH, sizeof(noffH), 0);
    if ((noffH.noffMagic != NOFFMAGIC) && 
		(WordToHost(noffH.noffMagic) == NOFFMAGIC))
    	SwapHeader(&noffH);
    ASSERT(noffH.noffMagic == NOFFMAGIC);

    size = noffH.code.size + noffH.initData.size + noffH.uninitData.size ;
    numPages = divRoundUp(size, PageSize) + divRoundUp(MAX_THREADS*UserStackSize,PageSize); // magic number should remove
                                                // we need to increase the size
						// to leave room for the stack
    size = numPages * PageSize;

    ASSERT(numPages <= NumPhysPages);		// check we're not trying
						// to run anything too big --
						// at least until we have
						// virtual memory

    DEBUG('a', "Initializing address space, num pages %d, size %d\n", 
					numPages, size);
// first, set up the translation 
    pageTable = new TranslationEntry[numPages];
    for (i = 0; i < numPages; i++) {
	pageTable[i].virtualPage = i;	// for now, virtual page # = phys page #
	pageTable[i].physicalPage = pageMap->Find();
	pageTable[i].valid = TRUE;
	pageTable[i].use = FALSE;
	pageTable[i].dirty = FALSE;
	pageTable[i].readOnly = FALSE;  // if the code segment was entirely on 
					// a separate page, we could set its 
					// pages to be read-only
    }
    
// zero out the entire address space, to zero the unitialized data segment 
// and the stack segment
   // bzero(machine->mainMemory, size);

// then, copy in the code and data segments into memory
	RestorePageTable();
    if (noffH.code.size > 0) {
        DEBUG('a', "Initializing code segment, at 0x%x, size %d\n", 
			noffH.code.virtualAddr, noffH.code.size);
		int* physicalAddr;
		machine->Translate(noffH.code.virtualAddr, physicalAddr, noffH.code.size, FALSE);
        executable->ReadAt(&(machine->mainMemory[*physicalAddr]),
			noffH.code.size, noffH.code.inFileAddr);
    }
    if (noffH.initData.size > 0) {
        DEBUG('a', "Initializing data segment, at 0x%x, size %d\n", 
			noffH.initData.virtualAddr, noffH.initData.size);
		int physicalAddr;
		machine->Translate(noffH.initData.virtualAddr, &physicalAddr, noffH.initData.size, FALSE);
        executable->ReadAt(&(machine->mainMemory[physicalAddr]),
			noffH.initData.size, noffH.initData.inFileAddr);
    }

}

//----------------------------------------------------------------------
// AddrSpace::~AddrSpace
//
// 	Dealloate an address space.  release pages, page tables, files
// 	and file tables
//----------------------------------------------------------------------

AddrSpace::~AddrSpace()
{
	// Deallocate all of our pages in physical memory.
	for (unsigned int i = 0; i < numPages; i++) {
		pageMap->Clear(pageTable[i].physicalPage);
    }
    delete pageTable;
}

//----------------------------------------------------------------------
// AddrSpace::InitRegisters
// 	Set the initial values for the user-level register set.
//
// 	We write these directly into the "machine" registers, so
//	that we can immediately jump to user code.  Note that these
//	will be saved/restored into the currentThread->userRegisters
//	when this thread is context switched out.
//----------------------------------------------------------------------

void
AddrSpace::InitRegisters()
{
    int i, stackIndex = stackMap.Find();
	DebugInit("b");
	DEBUG('b', "Stack Index = %d.  ", stackIndex);
	if (stackIndex != -1) {
		for (i = 0; i < NumTotalRegs; i++)
		machine->WriteRegister(i, 0);

		// Initial program counter -- must be location of "Start"
		machine->WriteRegister(PCReg, 0);	

		// Need to also tell MIPS where next instruction is, because
		// of branch delay possibility
		machine->WriteRegister(NextPCReg, 4);

	   // Set the stack register to the end of the address space, where we
	   // allocated the stack; but subtract off a bit, to make sure we don't
	   // accidentally reference off the end!
		machine->WriteRegister(StackReg, (numPages * PageSize - 16) - stackIndex*UserStackSize);
		// Mark all the pages for this stack in the pageTable as used.
		for (int j = 0; j < UserStackSize/PageSize; j++) {
			pageTable[numPages - stackIndex*UserStackSize/PageSize - j].use = TRUE;
		}
		DEBUG('b', "Initializing stack register to 0x%x\n", (numPages * PageSize - 16) - stackIndex*UserStackSize);
	}
	else {
		DEBUG('a',"ERROR: Could not allocate a stack for thread %s. Stack limit reached.\n",currentThread->getName());
	}
}

//----------------------------------------------------------------------
// AddrSpace::SaveState
// 	On a context switch, save any machine state, specific
//	to this address space, that needs saving.
//
//	Need to save all the registers.
//----------------------------------------------------------------------

void AddrSpace::SaveState() 
{
	for (int i = 0; i < NumTotalRegs; i++) {
		machine->WriteMem(machine->ReadRegister(StackReg), 4, machine->ReadRegister(i));
		machine->WriteRegister(StackReg, machine->ReadRegister(StackReg)-4);
	}
}

//----------------------------------------------------------------------
// AddrSpace::RestoreState
// 	On a context switch, restore the machine state so that
//	this address space can run.
//
//      tell the machine where to find the page table.
//		reload all the register values with the saved ones.
//----------------------------------------------------------------------

void AddrSpace::RestoreState() 
{
	for (int i = 0; i < NumTotalRegs; i++) {
		int regvalue;
		machine->ReadMem(machine->ReadRegister(StackReg), 4, &regvalue);
		machine->WriteRegister(i, regvalue);
		machine->WriteRegister(StackReg, machine->ReadRegister(StackReg)+4);
	}
    RestorePageTable();
}

void AddrSpace::RestorePageTable() {
	machine->pageTable = pageTable;
    machine->pageTableSize = numPages;
}

int AddrSpace::NumAvailStacks() {
	return stackMap.NumClear();
}

void AddrSpace::ClearStack() {
	int stackIndex = ((numPages*PageSize) - (machine->ReadRegister(StackReg)+16))/UserStackSize;
	for (int i = 0; i < UserStackSize/PageSize; i++) {
		if (pageTable[numPages - stackIndex*UserStackSize/PageSize - i].valid == TRUE) {
			pageTable[numPages - stackIndex*UserStackSize/PageSize - i].use = FALSE;
		}
	}
}

void AddrSpace::SetProcessID(int id) {
	processID = id;
}
